1. Field of the Invention
The present invention relates to a vehicle drive assist system that recognizes a front vehicle and a rear vehicle and prevents a subject vehicle from colliding with the front vehicle and the rear vehicle.
2. Description of the Related Art
In recent years, various techniques have been suggested for vehicles, the techniques which detect a front vehicle by using a front recognizer, such as a camera or a laser radar, and to avoid a subject vehicle from contacting the front vehicle, assist drive of the subject vehicle by providing a predetermined alarm or automatic brake control. Such techniques have been practically used. In addition, a technique has been suggested, which detects a rear vehicle and provides alarm control by taking into account the rear vehicle.
For example, Japanese Unexamined Patent Application Publication No. 2007-207047 has disclosed a technique for a vehicle stop alarm device, which detects a proximity state of a subject vehicle to a stop-requested point based on a current position, the stop-requested point, and a subject vehicle speed, determines a collision risk based on a relative positional relationship between the subject vehicle and at least one of a front vehicle and a rear vehicle, and provides alarm control based on the proximity state and the collision risk.
A driver can relatively easily recognize a distance between the front vehicle and the subject vehicle, a relative speed between the front vehicle and the subject vehicle, and a brake operating state of the front vehicle. However, the driver recognizes the rear vehicle only through a mirror, and a time the driver looks at the mirror must be short. It is difficult to recognize a distance from the subject vehicle to the rear vehicle, a relative speed between the rear vehicle and the subject vehicle, and a brake operating state of the rear vehicle. Regarding the above-mentioned problem, the above-described technique of the alarm device disclosed in Japanese Unexamined Patent Application Publication No. 2007-207047 controls the alarm by using the collision risk merely based on the relative positional relationship between the subject vehicle and at least one of the front and the rear vehicle, it is suspected that the alarm is not properly provided.